Known conventional methods for producing an alkyl 5-methyl-5-hexenoate (5-methyl-5-hexenoic acid alkyl ester) include a method of using an ene reaction of an acrylic acid ester and isobutene (see Non-Patent Reference 1) and a method in which a decarboxylation reaction of dimethyl(3-methyl-3-butenyl)malonate is carried out using 2-fold mol of water and equivalent mol of sodium chloride as a nucleophile in N,N-dimethylformamide (DMF) as a solvent (Krapcho reaction) (see Non-Patent Reference 2).